The Santa Clara County Parks Department has shut down a portion of the Almaden Quicksilver County Park in South San Jose indefinitely after a landfill company released a noxious byproduct of methane gas into a creek.

The Regional Water Quality Control Board called the parks department’s environmental officer Tuesday about an “uncontrolled release of condensate liquid” at the Guadalupe Rubbish Disposal ﻿landfill in San Jose on Guadalupe Mines Road.

The exact nature of what’s in the spill has not been made clear. But O’Connor said it is a “condensate,” a byproduct of methane gas formed at the landfill, which is why it’s also called a “landfill gas.”

The landfill’s tank overflowed twice Tuesday, according to the parks department, into a sediment pond that also overflowed into McAbee Creek at the northern end of the park near the Senador Mine. The parks department decided to close off a few trails near the McAbee entrance until further notice. Almaden Quicksilver County Park comprises more than 4,100 acres and used to be a major mercury-mining area in the 19th century.

Jennifer Andrews, a spokeswoman for Waste Management, the owner and operator of the rubbish company, was not immediately available for comment. O’Connor said the company was responding to the cleanup requirements, but no specifics have yet been provided.

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